Most of the recent terminals (also known as User Equipments (UEs)) are multi-mode terminals that may use different wireless communication technologies such as Wireless Local Area Network (WLAN), cellular communication, Bluetooth, and the like. Typically, the multi-mode terminal may access one wireless communication network to receive services, and when desiring to access another wireless communication network, the multi-mode terminal may perform handover from the existing wireless communication network to a new wireless communication network. Therefore, there is a need for the network structure and various technologies for the continuity of services when a terminal moves from one wireless communication network to another wireless communication network. In 3rd Generation Partnership Project (3GPP), the network structure and various technologies needed for the terminal's movement between a 3GPP wireless communication network and a WLAN network are especially called interworking WLAN. The multi-mode wireless communication technology has evolved not only to use one communication technology at a time, but also to use multiple wireless communication technologies at the same time. The use of multiple wireless communication technologies simultaneously thereby increases transfer rates per unit time or improves the reliability of the terminal.
In wireless communication, the spectral band is very rare resources. A licensed band represents a frequency band that is exclusively licensed to a specific operator to provide specific wireless services. On the other hand, an unlicensed band (or license-exempt band) represents a frequency band that is not allocated to a specific operator, but is opened so that all entities meeting the predefined requirements may use the frequency band. The licensed band may be fundamentally prevented from undergoing interference caused by wireless services of other operators, since only the licensed or authorized operator may provide wireless services in the licensed band. However, interference control is a very important factor for the unlicensed band since the unlicensed band is a frequency band that any operators or individuals may use in an open way.
WLAN that uses Wireless Fidelity (Wi-Fi) which is the typical wireless communication technology used in the unlicensed band may operate based on Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA). Specifically, in the WLAN, when a terminal needs to start transmission, a Clear Channel Assessment (CCA) interface of a physical layer may first perform a carrier sense operation of determining whether a wireless channel is in an idle state. The WLAN may start the transmission, if it is determined that the wireless channel is in the idle state for a specific time (e.g., Distributed Inter Frame Space (DIFS)). However, if the wireless channel is not in the idle state for the specific time, the WLAN needs to wait until the ongoing transmission in the wireless channel is completed.
In addition to the carrier sense operation that is performed in the CCA interface of the physical layer, a Virtual Carrier Sensing (VCS) operation may be performed in a Media Access Control (MAC) layer. A Duration field of a MAC header of a Wi-Fi frame may include information about required transmission time for the frame and a series of the Wi-Fi frame's succeeding frames. Therefore, upon receiving the frame, a terminal may determine that the wireless channel is busy or in use, regardless of the results of the carrier sense operation that has been performed in the CCA interface for the time corresponding to the time information included in the Duration field. In this way, the Wi-Fi frame and a series of the Wi-Fi frame's succeeding frames may be securely transmitted.
As described above, an unlicensed band is a frequency band that is not allocated to a specific operator, but is opened so that all entities meeting the predefined requirements may use the frequency band. Therefore, communication technology that uses the unlicensed band is required to design a protocol that considers interference from other services. If the communication technologies (e.g., cellular communication and the like), which were originally designed without assuming that the communication technologies may be used in the unlicensed band, are used in the unlicensed band, their transmission may affect transmission of the existing WLAN system.
Accordingly, a method and apparatus for performing data communication using an unlicensed band without the impact of interference from other services in a common wireless communication system is desired.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.